Infection Control & Hospital Epidemiology
allows multiple samples to be taken from a single venipuncture. The best practice is to discard the double-end needle and tube holder as a single unit into a sharps container to minimize the risk of nee- dlestick injury. The World Health Organization (WHO)12 and the Occupational Safety and Health Administration (OSHA) recom- mend theuse ofasingle-usedisposabletubeholdertoreducethe risk of needlestick injury.13,14 Manufacturers of tube holders either recommend using such devices as single use or performing disin- fection with bleach after each use as reusable device.15,16 Such tube holders are still available in the market and reusing tube holder without disinfection between patients has been a common practice in our public hospitals since its introduction. Disinfection was only advised if there was visible blood in the tube holder. Here, we report an outbreak of nosocomial transmission of HCV and our investigation of the reusable tube holder as a nosocomial source of infection because previous surveillance data in Hong Kong indi- cated a low incidence of HCV positivity among new blood donors.
Methods Epidemiological investigation
An investigation of HCV infection in the liver transplant unit (a mixed-gender ward of 28 beds) at Queen Mary Hospital, Hong Kong, was conducted when a case of HCV genotype 6a infection wasidentified14monthspostliver
transplant.The liverdonor and all used blood products after the transplant were HCV negative, which excluded the liver donor and blood products as the source. Since the incidence of HCV antibody positivity among the new
blood donor were 0.04% (17 HCV new cases per 48,769 blood donor) and 0.06% (21 HCV new cases per 35,848 blood donor) in 1991 and 2016, respectively,17 an outbreak was defined as 1 or more patients with newly diagnosed nosocomially acquired HCV (index case) linked epidemiologically to a known HCV carrier (potential source patient) associated with an environmental source during the incubation period, as described in our previous outbreak investigations.18–21 A case of nosocomially acquired HCV was defined as (1) baseline anti-HCV antibody and HCV RNA negativity, followed by (2) anti-HCV antibody seroconver- sion or a detectable HCV RNA. The index case was interviewed by infection control nurse for personal risk factors for community acquisition of HCV, such as body piercing, acupuncture, tattoo, unprotected sexual contact, and intravenous drug abuse. More- over, 24 ward-based medical, nursing, and supporting staff in the unit were interviewed and observed by an infection control nurse for recent changes in clinical practice, patient care proce- dures and staff-to-patient ratio retrospectively. Ethics approval was obtained from the institutional review board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster.
Medical record review and contact tracing
The medical record of the index case was reviewed for all patient- care episodes with risks of percutaneous or mucosal transmission: phlebotomy, blood transfusion, finger pricking for glucose sticks, endoscopy, peripheral and central intravenous catheter insertion, and intravenous injections of medications, including multiple- dose drug vials. Contact tracing was conducted to search for all known HCV carriers present in the same ward with the index case during the incubation period, as previously described.22–24A contact case was defined as a patient who stayed in the same ward as the index case. All contact cases who screened positive for
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HCV could be a potential source patient or a secondary case. Archived blood samples, if available, were retrieved in the laboratory for anti-HCV antibody and HCV RNA viral load assays. Contact cases without archived blood samples were called back for HCV testing.
Environmental surveillance
Environmental sites with direct or indirect contact of blood were collected for detection of HCV RNA. The phlebotomy trolley, tray, reusable tube holders of the vacuum extraction tube system for phlebotomy, and blood-glucose monitoring machine were swabbed using rayon-tipped Copan swab applicators (Copan, Brescia, Italy). The swabs in viral transport medium were sent for testing immediately. Environmental samples with detectable HCV RNA by RT-PCR were subjected to Sanger sequencing and phylogenetic analysis along with those of index and source patients.25
In vitro demonstrations during simulated phlebotomy
To ascertain the possibility of HCV transmission through con- taminated reusable tube holders, several in vitro experiments were performed. To demonstrate HCV transmission through reflux from a contaminated reusable tube holder toward the patient side, an in vitro experiment was performed in triplicate using HCV- contaminated plasma. First, 5mm of the rubber sleeve capping the sleeved-needle was dipped into plasma from a known HCV- positive patient with an HCV RNA viral load of 1×106 IU/mL. Then, the double-end needle was screwed onto the tube holder. The skin-needle was inserted into a tube fully filled with HCV- negative EDTA blood (tube A) at atmospheric pressure, to mimic the venous side of a patient. An empty EDTA vacuum-specimen tube (tube B) was then plunged onto the sleeved-needle by fitting into the tube holder, thus mimicking the phlebotomy process. An in-and-out motion was performed 3 times to simulate phlebotomy using 3 vacuum-specimen tubes. Blood samples from tubes A and B were tested for HCV viral load. Next, we used radionuclide studies with 99mTc pertechnetate (99mTcO4) to simulate HCV-contaminated blood. This experi- ment was repeated 3 times by light smearing of the tip of the sleeved-needle with gauze containing a few drops of 99mTcO4. The sleeved-needle was then fitted onto the tube holder between the 2 detector heads of a dual-head SPECT/CT gamma scanner ready for acquisition of radioactivity readings. A saline-prefilled EDTA vacuum-specimen tube (mimicking the engorged vein of patient) was inserted onto the skin-needle, while empty vacuum-specimen tubes were inserted through the tube holder onto the sleeved- needle and then removed 3 times to simulate phlebotomy. Ima- ging with static acquisition was conducted for 200 seconds. To simulate and image the point of release of the tourniquet, a follow-up experiment was performed by inserting the skin-needle already fitted on the tube holder into a 100-mL saline bag under gentle manual pressure (simulating venous pressure). An EDTA vacuum-specimen tube containing a mixture of 99mTcO4 and saline was plunged into the sleeved-needle inside the tube holder and then withdrawn after 3 seconds to simulate phlebotomy. The manual pressure on the saline bag was released to simulate the release of the tourniquet. Imaging of the saline bag and tube holder was again conducted for 200 seconds. Finally, we conducted in vivo testing to demonstrate the change
in venous blood pressure during the release of a tourniquet at the end of phlebotomy (see online Supplementary File 1).
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